The present invention relates generally to rotary electric machines, and specifically relates to a rotary electric direct current machine as specified in the preamble of the accompanying claim 1, a rotor for such a rotary electric direct current machine according to the preamble of claim 9 and a rotor coil support for a rotor of a rotary electric direct current machine and according to the preamble of claim 17.
The development within the general area of rotary electric machines is presently directed towards an ever higher performance utilization, that is a higher and higher output in terms of power and torque, for given machine sizes. One condition of such higher performance is that the cooling of the machine can be made correspondingly more effective, and consequently intense development is carried out in this purpose.
With regard to direct current machines, great improvements have for instance been achieved in the rotor cooling, and perhaps most of all through the advances in the cooling of the rotor plate stack that have been made through the principles described in our Swedish Patent Application no. 9900227-1. These principles relate to the symmetrical positioning of the rotor cooling channels relative to the magnetic flow paths in the rotor, and thereby to the provision of cooling channels in a greater number and closer to the outer circumference of the rotor.
Through this optimization of the cooling of the actual rotor plate stack the development has been carried so far that other parts of the machine, which parts have earlier been regarded as having a satisfactory cooling, are now instead limiting the possible power output of the machine. One such so-called xe2x80x9chot spotxe2x80x9d in the machine is those parts of the rotor coils positioned in axial grooves of the rotor, which lie outside the actual rotor plate stack.
In conventionally designed direct current machines, see the enclosed FIG. 1, the major portion of the rotor coil ends 2, that is the end windings, of the rotor 1 lie thermally isolated between a coil support 3 and a rotor coil bandage 4. The general kind of rotor coil support 3 that forms the basis of this invention consists of a relatively thin and light ring of synthetic resin (plastic) or metal that is attached directly to the rotor, in its outer region. In contrast thereto, heavy and material consuming and often cast coil supports also exist within this technical field. The latter type is supported on the rotor shaft 5 and quite different conditions apply thereto.
In rotor coil supports of the kind in question here, it has been quite satisfactory up to now to let the rotor coil ends be cooled by cooling air only on the rotor coil back 6 that is accessible to the cooling air. The conductor length in the rotor coil back constitutes approximately only 20-25% of the total length in the rotor coil ends. Bearing this in mind and considering the above described, general development within this field, said method is not sufficient for allowing the machine taken as a whole, to come even close to being able to benefit from the above described progress that has been achieved regarding the cooling of the rotor plate stack.
To sum up, it may be established that the conventional rotor coil supports have worked well in themselves under the conditions that they have been intended for. However, they can not meet the ever-higher demands for the cooling of the machine taken as a whole. In other words, the intense development and thereby optimizing of the cooling of the actual rotor plate stack has resulted in that the above mentioned parts of the machine have come to constitute an obstacle to a maximum power output.
A basic object of the invention is therefore to provide, in a rotary electric direct current machine, an improvement in the cooling of the coil ends or end windings of the rotor coils, that is proportional to the development that has taken place with regard to the cooling of the rest of the machine. In particular, the object is to provide this improved cooling without any negative effect upon the coil support in other respects, and with simple and inexpensive means.
In accordance with the invention this is achieved by providing the rotary electric direct current machine with a rotor coil support having a surface area that is considerably enlarged in relation to its circumference, as is specified in the characterizing portion of claim 1. Regarded as a whole, this results in a significant improvement of the cooling capacity by providing efficient cooling also of the parts of the rotor coil ends/end windings bearing on the rotor coil support.
According to an advantageous embodiment of the basic aspect of the invention the rotor coil support is provided at its inner side with a configuration enlarging its surface area. This configuration has the shape of cooling fans or flanges directed generally radially inwardly towards the rotor shaft. This feature of the invention is specified in the enclosed claim 2. This feature achieves the desired cooling of the coil ends in a particularly efficient way.
In an embodiment of the invention that is specified in claim 3, the cooling flanges are in themselves provided with a grooved or serrated surface, whereby is achieved a further enlargement of the surface and a further improved cooling capacity.
In accordance with an embodiment specified in claims 4 and 5, at least some of the cooling flanges are configured so that they together serve as attachments for balance weights. In this manner the cooling flanges serve the additional purpose of balancing of the rotor. Hereby, the traditionally provided balance disc or corresponding means supported on the rotor shaft can be eliminated altogether.
A further advantageous embodiment of the invention is specified in claim 6. In accordance therewith a centering and fixing of the rotor coil support relative to the rotor is achieved by the fact that a number of the cooling flanges of the rotor coil support are provided with seats for guide pins that may be connected to the axial end of the rotor.
In accordance with a further embodiment of the invention the rotor coil support is formed by a number of interconnectable segments, such as is specified in claims 7 and 8. Such a design contributes to the lowering of the manufacturing cost, since the extrusion tool may be manufactured at a significantly lower cost.
In accordance with another aspect of the invention a rotor for a rotary electric direct current machine is provided. Said rotor is provided with a rotor coil support having a surface area that is considerably enlarged in relation to its circumference, as is specified in the characterizing portion of claim 9. Such a rotor can be useful both as a spare part for a direct current machine or as a replacement part in connection with the upgrading of an existing machine.
Embodiments of this second aspect of the invention are specified in the dependent claims 10-16.
In accordance with a further aspect of the invention a rotor coil support is provided, having a surface area that is considerably enlarged in relation to its circumference, as is specified in the characterizing portion of claim 17. Such a rotor coil support can be useful both as a spare part for a direct current machine or as a replacement part in connection with the upgrading of an existing rotor.
Embodiments of the last mentioned aspect of the invention are specified in the dependent claims 18-25.
Further objects, features and advantages of the invention are explained more closely in the following description of exemplifying embodiments thereof.